1. Field of the Invention
The present invention relates to a nonaqueous electrolyte battery, and a battery pack and a vehicle provided with this nonaqueous electrolyte battery.
2. Description of the Related Art
As shown in JP-A 5-151953 (KOKAI) and JP-A 2006-59690 (KOKAI), it is known that an improvement in the performance of a battery can be attained by knowing the state of particles in the battery electrode based on the measurement of the pore distribution of the battery electrode by using mercury porosimetry. In this case, JP-A 5-151953 (KOKAI) relates to an invention using, as the negative electrode active material, a mixture of a metal oxide and an insoluble and infusible base of a polyacene type skeleton structure having a specific surface area of 600 m2/g or more as measured by a BET method. On the other hand, JP-A 2006-59690 (KOKAI) relates to an invention using, as the negative electrode active material, a composite graphite material having a relatively small specific surface area of 1.5 to 5 m2/g as measured by a BET method.
When a lithium compound having a small ionic diffusibility in a solid is used as the negative electrode active material, it is difficult to develop a high power battery. However, it is known that high power can be attained by using microparticles of this lithium compound. These microparticles of a lithium compound pose the problem that they cause a large variation in the output characteristics of a battery depending on the production method of the battery, because they have the characteristic that they tend to be coagulated in a process of producing an electrode using these microparticles.
The nonaqueous electrolyte battery described in JP-A 2007-18882 (KOKAI) uses, as the negative electrode active material, lithium compound particles having a lithium ion absorption potential of 0.4V (vs. Li/Li+) or more and an average particle diameter of 1 μm or less. In JP-A 2007-18882 (KOKAI), during the manufacture of a negative electrode, a slurry is stirred strongly in a specified condition to reduce coagulation among lithium compound particles. It is described in JP-A 2007-18882 (KOKAI) that the edges of lithium compound particles are scraped away by this stirring to smooth the surfaces of these particles. JP-A 2007-18882 (KOKAI) also describes that, as a result, these lithium compound particles can be filled at a high density in a negative electrode. Therefore, the pore size diameter distribution is shifted to the smaller pore size diameter side, with the result that a first peak having a mode diameter of 0.01 to 0.2 μm and a second peak having a mode diameter of 0.003 to 0.02 μm appear in the log differential intrusion curve of the negative electrode, as measured using mercury porosimetry. JP-A 2007-18882 (KOKAI) describes that the cycle life of a nonaqueous electrolyte battery is improved by specifying the pore volume in each peak range.